1. Field of the Invention
The present invention relates to a fuel economy improvement assist device and a method of improving fuel economy by displaying the accelerator operation amount to a driver.
2. Description of the Related Art
In order to reduce the fuel consumption, various driving techniques such as avoiding sudden starting and acceleration, constant-speed driving, using higher gears, stopping engine idling are recommended. While many drivers keep the fuel economy in mind when driving, display devices that are used to display information to the drivers for improving fuel economy to further reduce the fuel consumption are known as below.
Japanese Patent Application Publication No. 2003-220851 (hereinafter referred to as “JP-A-2003-220851”) describes a display device that it is determined whether the actual operation is suitable for improving fuel economy when the driver selected a gearshift mode for improving fuel economy, and then a lamp is turned on when the actual operation is suitable for improving fuel economy. On the other hand, the lamp is turned off when the actual operation is not suitable for improving fuel economy. Therefore, the driver may be encouraged to operate suitably for improving fuel economy.
Japanese Patent Application Publication No. 2002-370560 (hereinafter referred to as “JP-A-2002-370560”) describes a display device that compares a calculated present fuel consumption to a recommended driving pattern specific to each vehicle, and then displays appropriate accelerator operation manners (i.e., appropriate, should be stopped, or over-depressed) in different colors. Therefore, the driver may be encouraged to operate appropriately after recognizing the displayed color.
However, the display device described in JP-A-2003-220851 merely determines a driving operation, and turns on and off the lamp. Thus, the displayed information may be insufficient. Because the lamp indicates only whether the driving operation is suitable for improving the fuel economy but provides no indication of the accelerator depression amount until the threshold for turning on or off the lamp is reached. Accordingly, the driver is not aware of how much further the accelerator pedal may be depressed. Therefore, even drivers who keep fuel economy in mind, may frequently use the low accelerator operation amount region, and may possibly maintain for a long time an accelerator operation amount where the fuel economy is poor. When the driver adjusts the accelerator depression in response to turning on and off of the lamp, the driver may frequently increase and decrease the accelerator depression around the threshold for turning on and off the lamp, which may reduce fuel economy.
The display device described in JP-A-2002-370560 calculates the instantaneous fuel consumption for comparison with the fuel consumption based on a recommended driving pattern. However, it is not possible to provide appropriate accelerator operation instructions to the driver before the fuel economy is reduced. For example, in the throttle valve control of the gasoline car, the engine may be controlled based on the detection of changes in the accelerator depression speed. However, according to the display device described in JP-A-2002-370560, the driver may not learn the way to avoid reducing fuel economy in response to the accelerator depression because the causes that lead to be reduced fuel economy are not displayed to the driver. In addition, the display device described in JP-A-2002-370560 provides no indication of the accelerator depression amount until the threshold for displaying “appropriate” or “over-depressed” is reached, as similar to JP-A-2002-370560. Accordingly, the driver is not aware of how much further the accelerator pedal may be depressed.